In many industrial processes and in fluid production systems, a slurry of solids suspended in a liquid is produced and it becomes necessary to separate the solids from the liquids so that each material may be treated in ways that will make disposal of the treated materials both economical and environmentally effective. In most such processes or systems, the slurry material is fed to a filter apparatus in the form of at least a pair of plate members with internal space separated by a filter media of some form. The plate members are pressed together at mating surfaces with the filter media between the mating surfaces and spread across the interior space separating the upper plate from the lower plate. Slurry materials are fed into the upper plate and filtrate liquids are taken away from the lower plate leaving behind the solids of the slurry accumulated on the filter media. After a sufficient amount of slurry has been treated to accumulate solid materials, the plates are separated and the filter media is replaced and the filtration process is repeated with a clean filter media. The filtrate fluid and solids are then separately treated or disposed of in an acceptable manner.
In some slurry filtering processes the fluid carrier in the slurry is toxic or noxious so that it is desirable to avoid leakage of the slurry or the filtrate to the outside of the mating surfaces of the plates. Many systems of pressing the mating surfaces together have been suggested, but none so far seem to be effective. Several examples of the systems for sealing the mating surfaces have suggested formations at the mating surfaces of filter plates with air or liquid pressure supplied to those formations to prevent fluid flow and others have suggested applying vacuum to the suggested formations. Such systems and formations are shown in U.S. Pat. No. 3,443,695 where a groove is formed in the mating surface of the lower plate and air or liquid pressure or vacuum is supplied to the groove; U.S. Pat. No. 3,499,532 where two grooves are provided in the mating surface of the lower plate with one groove having a pressure higher than atmospheric and the other open the the atmosphere; U.S. Pat. No. 3,608,734 where a groove is formed in the mating surface of the upper plate and a vacuum is supplied to that groove; U.S. Pat. No. 4,267,060 where a groove is formed in the mating surface of the lower plate and a fluid (filtrate or inert gas) is supplied to the groove; and U.S. Pat. No. 4,664,813 where a groove is formed in the mating surface of the upper plate and air, under pressure, is supplied to the groove. None of these systems is completely effective in preventing leakage of fluids through the mating surfaces of the pressed together plates of a filter apparatus.
Most prior art systems where leakage occurs at the mating surfaces have resorted to impregnating the edges of the of the filter media to function as a gasket at the mating surfaces; however, even when used with the grooves of the prior art the prevention of leaking has been ineffective. Others have suggested O-rings or other gasket materials, but those systems are difficult to align and are still ineffective.
It is an object of the present invention to provide a formation of the mating surfaces of pressed together plates of a filter apparatus in a manner to substantially eliminate leakage between the mating surfaces.
A further object in accord with the preceding object is to provide a set of grooves in the mating surfaces that will permit the application of fluid pressures that will prevent leakage between the surfaces.
A further object in accord with the preceding objects is to provide mating grooves in the mating surfaces of pressed together plates with a fluid under pressure supplied to one groove and a fluid under vacuum applied to the other.